It's been a month since I started this log and here are the two most significant things I learned so far for printing objects:

The bed needs to be leveled carefully and first layer should stick well. If the first layer is compressed too much by the nozzle, then hot plastic, not having an escape path rises up in the barrel and forms a break to the filament movement, resulting in stepper missing steps and a deteriorated or ruined print. At least, this is what happens with my DIY AlFe + CuHotE extruder. If, to the contrary, the first layer is correctly sized then the whole print goes smoothly and no step is ever missed in the extruder.

Using a fan for PLA prints is a MUST(I haven't yet printed anything in ABS, mostly due to its smell)The 2mm tip in Sappho's bun hairstyle cannot be printed with out a cooling fan or slowing down the print significantly to allow for natural cooling:

0.25mm layers, 0.4mm nozzle.

Here are some objects printed today:

http://www.thingiverse.com/thing:14565

There are some artifacts due to Z-axis wobble. They can be seen in the small Sappho's chest. I've carefully adjusted the stepper motor screws to minimize wobble and the improvement shows in the bigger Sappho, though the problem is not yet eliminated. The bigger Sappho is just a scaled up version of the small, so both have the same amount of details.

I needed connectors for my DIY extruder. This made the gantry a plate of cable spaghetti. Time to tidy it up:

Before/after

I used a perforated PCB to mount the connectors. Usually the connectors go with the cable so that it can be easily removed, but I change the extruder frequently for measurements, so I put the connectors on the extruder and fixed the cable on the PCB. The PCB is mounted on a printed PLA base.The PCB is populated with additional connectors for a second extruder.

Tried a couple of quick solutions for a filament spooler but didn't like the result, so what's better than printing one?Well, trying to print a large object showed that the bed needed some levelling. Here's how I mounted the dial indicator:

I had to clean the V wheels of the X-axis with a cotton swab, because any dirt on them shows directly on the dial. This is the simple spooler I printed for a 125x200mm OD spool:

Solved a problem with the Z-axis end-stop not functioning properly: it was stopping before the end just after moving for a few mm. The whole z-axis had a problem too: couldn't move reliably but stopped at random points along the requested distance.

I suspected noise on the Z-axis stop wires, so I tried to make a simple RC low-pass filter incorporating the on-chip pull-up resistor at the digital inputs of the ATmega. The internal pull-up resistors are 20-50kΩ (per spec) so I figured that a 33nF capacitor that I had in hand would give a cutoff freq of about 137Hz and delay the real signal by about 4ms. So I soldered the capacitor at the PCB side of the limit switch wires and ... all z-axis problems disappeared at once.

Conclusion: There must be a serious noise problem with my built. That showed up early with the thermistor and persists until today, showing various symptoms.

On the good side of things, I printed the Venus of Willendorf- Bakutis Style thing at 150% scale (about actual real size, 116mm tall) and 0.25mm layers, 0.4mm nozzle @80mm/sec with acceleration X2000 Y4000. It took 02:08:39 and went flawlessly from start to end. This is the tallest thing I've printed so far.

Venus of Willendorf- Bakutis Style, Thingiverse.com

There is still a slight z-axis wobble that I need to eliminate that shows on the shiny parts of the print.

Thanks! I hope you find the rest of the parts and get on with printing, it's a lot of fan (and sorrow too)

Gijs wrote:Just wondering about the noise problems you had with the end stop: do you have your wires twisted?

No, they are inside the shielded cables. All cables I use are shielded, and signals go in different cables than motors, so theoretically the signal wires should not pick up EMI from the motors etc. but reality wants it differently. What's strange is that I use the normally closed connection of the limit switch so the signal wire is connected to the ground until the switch hits the end stop, at which time the pull-up resistor drives the signal to Vcc+. But it seems I'm getting the noise while the contact is closed i.e. on a grounded wire

At present I have gathered all cable shields and grounded them at the power input ground terminal. I have also grounded the gantry and the alu frame and checked that all connections are good. There might be something else though, that's gone unnoticed.

In time, I'll get the RAMPS boards caged in a metal box and see if it gets any better

dzach wrote:Thanks! I hope you find the rest of the parts and get on with printing, it's a lot of fan (and sorrow too)

Indeed, lots of fan, I got 3 already installed, one for the extruder, one for the bed and one for the RAMPS electronics.

I followed Gijs suggestion and twisted the stepper motor wires, together with a rearrangement of the electronics and a separate ground on the frame.Result:The problem of noise in the end stop wires is gone. Got rid of the extra filtering capacitor I installed as a work around for the problem too.Next I'll try installing Marlin again, which was not working properly, possibly due to the same noise problem.

Things aren't always the way they should be. Here is a photo with some ABS prints.

The T5 pulley was printed @240°C, 0.35mm layers, 70mm/s feedrate. Something is not right but what? The filament looks like it's been overheated.

The bottom test cube was printed @220°C, 0.25mm layers, 25mm/s feedrate. I thought that lowering the speed would probably result in better quality. Was I wrong! The plastic was sticky and felt like it had been boiling.

The top test cube was printed @185°C, 0.26mm layers, 150mm/s feedrate. That's right, 185°C. I didn't expect it to print at all, after all PLA has a lower extrusion temperature (I can't print PLA at temperatures lower than 180°C) but came out great in comparison with the other two.

While testing this ABS filament I was able to extrude it @135°C !! I repeated the test many times; at 250°C the plastic makes sounds like frying potatoes ! At 150°C it extrudes happily and silently complete objects.

Conclusion: Every batch of material should be individually tested.

Story 2:

I was using Slic3r for some parts that involved some 3mm holes and a 22mm one to take a press-fit 608z bearing.

No matter what I did, the holes were coming out the wrong size; I could either get the 3mm right or the 22mm right but not both of them at the same time. In this thread I described the problem. As it turns out, Slic3r has a feature/bug that shrinks the holes that cannot be turned off, at least in the last version 0.8.3.

I tried Skeinforge and finally managed to print the part correctly. I've been using Skeinforge since then which, although its user interface can be intimidating to the new-comer, gives a lot more control over the result.